The increased costs of disposing material in landfills has intensified the need for developing cost effective machines for reducing the volume of waste material.
Hammermills have conventionally been employed to reduce the volume of waste material. Conventional hammermills have a shaft which is rotatably driven about a longitudinal axis. A plurality plates are mounted in longitudinally spaced relation along the length of the shaft. A plurality of swinging hammers are pivotally mounted between the plates on pivot shafts.
Upon rotation of the shaft, the hammers are swung radially outward from the shaft such that an impact zone is formed about the shaft. The material to be reduced is introduced into the impact zone and impacted by the swinging hammers. The swinging hammers repeatedly impact the material within the impact zone thereby crushing and grinding the material such that the material volume is reduced.
Due to a variety of factors, conventional hammermills employing pivotally mounted hammers have relatively short useful lives. For example, one factor which negatively affects hammermills is the accumulation of dirt and debris between the hammers and the plates and along the pivot shafts of the hammers. The accumulation of dirt and debris causes excessive wear of the hammers, plates and pivot shafts. Additionally, the material build-up frequently interferes with the proper pivotal motion of the hammers.
Another factor which shortens the life of conventional hammermills relates to the fact that the hammers are not always centered between the plates. The improper centering of the hammers allows contact between the hammers and the plates as the hammers are pivoted which causes premature wearing of the plates and hammers. Additionally, if the centering problem is severe, the hammers may become jammed between the plates such that the hammers are no longer free to pivot.
An additional factor causing premature wear in conventional hammermills having pivoting hammers relates to recoil impacts between the hammers and the main shaft. When conventional hammermill hammers are used to crush hard material such as stone, the intense reactionary forces caused by impact with the hard material causes the hammers to recoil and sharply impact the main shaft. This dual impact of the hammers significantly shortens the life of the hammers.
A further cause of wear in conventional hammermills is the presence of long and thin material such as string, magnetic tape and wire in the material to be reduced. The long and thin material has a tendency to wrap between the hammers and the plates thereby interfering with the pivotal motion of the hammers and shortening the useful life of conventional hammermills.
What is needed is an improved hammermill having a longer useful life and requiring reduced maintenance. What is also needed is a hammermill which prevents debris from accumulating between the hammers and the plates. What is additionally needed is a hammermill having centered hammers. What is further needed is a hammermill which brakes the recoil of the hammers. Moreover, what is needed is a hammermill which cuts material that becomes wrapped between the hammers and the plates.